Probing Canada's Three Oceans from the Surface to the Seabed Reveals Connectivities to Global Change

Global climate change and variability are anticipated to have the greatest impacts at high-latitudes. Many of these impacts are already apparent including declining sea ice, changes in the distribution of fish and marine mammals, and related impacts on traditional Inuit subsistence culture.

Other less visible but significant changes are underway in the Arctic Ocean and the bordering subarctic Pacific and Atlantic. To learn more about these changes, Fisheries and Oceans Canada embarked on The Canada’s Three Oceans (C3O) project (2007-2011), an International Polar Year (IPY) study led by Fisheries and Oceans Canada oceanographer Dr. Eddy Carmack of the Institute of Ocean Sciences.

“The Arctic Ocean is closely connected to the global system and must be observed accordingly,” says Dr. Carmack. “Aboriginal people will tell you that everything is connected to everything and we’re starting to learn how that connectivity really works.”

Multidisciplinary baseline data

In partnership with the ongoing international Joint Ocean Ice Study (JOIS), the C3O team — including scientists from Canadian and foreign governments as well as academia — set out to gather integrated, multidisciplinary baseline information on the physical, chemical and biological structure of subarctic and Arctic waters around Canada. This baseline will provide:

• a solid foundation for assessing and quantifying ongoing and future changes to both the shelf and basin regions of the western Arctic Ocean;
• valuable knowledge for addressing emerging issues such as warming, ice cover retreat, acidification, species invasion and hypoxia; and
• a firm basis for practicing good governance and decision-making related to the management and conservation of species and for adapting to the changing Arctic.

Since 2007, the C3O team has collected data from the surface to the seabed along a 15,000-kilometre stretch of marine Canada from the eastern Pacific, through the Arctic to the western Atlantic. More than 40 studies under the auspices of C3O probed these waters from the smallest organisms (viruses) to the largest (whales). Such varied research was made possible with the help of two Canadian Coast Guard icebreakers and crews that carry out annual missions encircling Canada twice yearly.

Ocean warming

C3O research identified changes already underway in the Arctic Ocean, including ocean warming and related structural changes from the surface to the bottom.

"The upper 30 to 40 metres are warming due to their direct connection with the atmosphere, and the layer below is warming due to warmer waters pouring in from the Pacific," says Dr. Carmack. "At even deeper levels between 200 and 2,000 metres, warming — by as much as 0.5oC — is the result of inflow from the Atlantic Ocean, and the bottom is warming because of geothermal heating. So the Arctic Ocean is a system that is changing, but not in isolation from the rest of the world. That's where connectivity comes in."

Waters of Atlantic origin, in particular the Fram Strait Branch (FSB) — a deep ocean channel between Greenland and Spitsbergen that connects the Nordic Seas to the Arctic Ocean — have warmed by as much as 0.5ºC since the year 2000. Ecosystem changes are likely to be greatest in the upper seasonal layer, to 50 metres, where substantial temperature increases are associated with ice removal and lowered albedo, the amount of solar radiation reflected by the Earth's surface. This may push organisms in the Arctic beyond their temperature limits or lead to oceanic communities that favour smaller micro-organisms. Regional warming may also lead to the break-down of current barriers and invasion of species not usually found in Arctic Ocean waters.

Ice Tethered Profilers (ITP)s are among several tools now available to scientists for gathering data on changes in the Arctic marine environment. An ITP is a 700-metre instrumented line that hangs beneath the ice surface to measure salinity, temperature and depth. Data collected by ITPs are transmitted to a surface buoy which relays the data back to shore via satellite, enabling researchers to view the latest information from this floating station on the internet. Ice Tethered Profilers are operational for about two years, moving with the ice to collect data even in areas that would be difficult to reach by ship, particularly in the winter. These profilers are part of the U.S. Woods Hole Oceanographic Institution component of the Canadian Arctic program.

Declining sea ice

"Sea ice is retreating and thinning. It is also looser, gets blown around more easily by wind and it's dragging the water underneath it as it moves," says Dr. Carmack.

During the IPY field years of 2007 and 2008, summer sea-ice extent in the Arctic reached a record-breaking minimum. There was also a dramatic decline in the extent and thickness of multi-year (older ice). The team identified and monitored oceanographic processes, associated with the inflow of Pacific-origin water, that are affecting sea-ice extent. Sea ice melting also results in increased volumes of low salinity and low-alkalinity (increased acidity) waters accumulating in the Beaufort Gyre — a clockwise circulation of surface water in the Beaufort Sea north of Alaska — with major biological implications.

An accelerated hydrological cycle combined with greater ice melt in summer is increasing upper ocean stratification because sea ice, which is fresh water, is lighter and doesn't mix well with saltier, deeper ocean water. Increased stratification impedes mixing of ocean layers, which is the mechanism that drives the upward movement of nutrients to the surface layer where plankton, the foundation of the Arctic food chain, grows in the sunlit euphotic zone. Reduced mixing may inhibit the amount of nutrients that reach the surface, potentially altering food webs.

Altered ocean circulation and advection?

Shifting ocean currents, fronts and water mass boundaries also play an important role in global change. "As ocean fronts change so do the domains in which the biota live," says Dr. Carmack.

One example of altered circulation is the apparent intensification and southeastward shift of the Beaufort Gyre during the 2000s. C3O findings also point to changes within the Arctic caused by advective processes (the horizontal flow of sea water as a current) originating in subarctic regions. For example, significantly warmer Atlantic-origin water from the Fram Strait Branch reached the western Canada Basin (a large sub-marine basin in the Arctic Ocean) in 2002 and spread across most of the southern basin interior by 2007. The advection of subarctic water masses, and modification upon entering the Arctic Ocean and moving across the pan-Arctic system, has fundamental impacts on ice cover, ocean properties and ecosystem dynamics.

"There is concern that the increased discharge of fresh water from the Arctic may slow thermohaline circulation, a global ocean circulation cell in which water from low latitudes moves into high latitudes and releases heat to keep the earth's climate system stable," says Dr. Carmack.

Acidification in the Arctic Ocean

"Ocean acidification is an emerging concern, and the Arctic is where this is happening the fastest and has now reached critical levels," says Dr. Carmack.

About one-third of the carbon dioxide (CO₂) released by human activities since the beginning of the Industrial Revolution in the 1800s has been taken up by the oceans. As CO2 dissolves in surface waters it forms carbonic acid, lowering the pH of ocean waters so they are more acidic. In the Arctic Ocean, acidification is exacerbated by the continued addition of low alkalinity sea ice meltwater to the seasonal mixed layer.

The most direct biological impact of lower pH will be on organisms that form calcium carbonate (CaCO₃) shells and skeletons, because a decline in pH increases the solubility of CaCO₃. These organisms include shellfish, corals and some phytoplankton and zooplankton. C3O research revealed that in 2008, the upper waters of the Canada Basin had already become undersaturated with respect to aragonite, a relatively soluble form of CaCO₃. When water is undersaturated with aragonite the mineral will tend to dissolve, affecting calcifying organisms and the composition of marine ecosystems in general.

Engaging Northern communities in ongoing monitoring

The original and ongoing goal of C3O is to gather data over a long enough time period to quantify change. Within the coming decades, the research team hopes to turn over a major portion of C3O monitoring methods to inter-connected local coastal communities so they can carry out as much marine monitoring as possible to aid ongoing climate change studies.